Factory original RARE Sig 551-2 SP SWAT manufactured in Switzerland, in .223/5.56 with 14 inch barrel (16 inches with permanent extension). Has 1/7 barrel twist to handle more modern ammo. A few of these were imported from Switzerland a few years ago as factory SBRs for Law Enforcement. These were then purchased by Michael’s Machines and had a permanent yet non destructive device added to the barrel to increase barrel length to 16 inches in order to remove them from the NFA Registry. Therefore it can be purchased as any other type of rifle. The extensions were installed where they could be removed with no damage to the gun for future SBR registration if desired.